One skilled in the art knows of a variety of coloring systems, depending on the required color result, for making available color-changing cosmetic agents, in particular for keratinic fibers such as e.g. human hair. For permanent, intense color results having corresponding fastness properties, so-called “oxidation” coloring agents are used. Such coloring agents usually contain oxidation dye precursors called “developer components” and “coupler components” that, under the influence of oxidizing agents such as hydrogen peroxide, form the actual dyes with one another. Oxidizing coloring agents are notable for outstanding, long-lasting color results. In addition to coloring, lightening of one's own hair color, resp. hair-bleaching, is a very special desire of many consumers. For this, the natural or artificial dyes coloring the fibers are usually decolorized oxidatively using corresponding oxidizing agents, for example hydrogen peroxide.
In order to provide satisfactory coloring and lightening performance, oxidative coloring agents resp. lightening agents generally require an alkaline pH during utilization; optimum results are achieved in particular at pH values between about 8.5 and about 10.5.
Until the present time, ammonia has been the alkalizing agent of choice for establishing these pH values. Not only can ammonia be used to establish the pH range necessary for dye formation, but ammonia also ensures swelling of the hair to a greater extent than all other known alkalizing agents. At the same time, ammonia acts as a penetration adjuvant.
The applications-engineering advantages associated with the use of ammonia are so numerous that despite its unpleasant, pungent odor, ammonia is used in a large number of commercial oxidative coloring agents.
Extensive efforts to reduce the ammonia odor are already known from the literature. A variety of possibilities exist for minimizing the odor: as a first possibility, the literature recites varying the alkalizing agent and thus partly or entirely replacing ammonia with odorless alternatives.
A plurality of formulations that employ a mixture of ammonia and monoethanolamine, or exclusively monoethanolamine, as an alkalizing agent already exist in the literature. Reducing the ammonia content often results, however, in poorer penetration of the dyes into the hair, which can be reflected especially in poorer gray coverage and poorer washing fastness.
Although complete or partial replacement of ammonia with alternative alkalizing agents has advantageous effects in terms of minimizing the odor of the coloring resp. lightening agents, it is associated with disadvantages in terms of the fastness properties of the color results obtained with the coloring resp. lightening agents. If a corresponding replacement of the alkalizing agent is made, the resulting losses in terms of coloring performance must be compensated for by optimizing the formulation.
WO 2006060570 and WO 2006060565 propose the use of carbonates or carbonate sources as alkalizing agents in order to furnish oxidative coloring agents with little odor impact. It is likewise known in the literature, however, that carbonates in combination with oxidizing agents can damage the hair to a greater extent. The additional damage to the hair brought about by carbonates may not be much of a problem when utilizing the coloring agent on untreated resp. undamaged hair, but in the case of persons who regularly color resp. bleach their hair it can add up to serious cumulative damage. If more intense lightening and/or regular coloring is desired, the use of carbonates therefore once again does not represent a feasible alternative.
A second possibility, in principle, for reducing ammonia odor consists in the addition of special perfume substances that are intended to mask the ammonia odor. This approach is taken, for example, in WO 2005/110499. Perfume substances can be unstable under alkaline storage conditions, however, so that the risk exists that the scents may become degraded or structurally modified during storage, which is also reflected in an unpredictable change in odor. Because corresponding changes often become perceptible only after several months or even years, the employment of new resp. unknown perfumes is considered problematic.
A third general possibility for reducing ammonia odor consists in optimizing the formulation. The idea here is to select the carrier constituents of the formulation in such a way that they ensure optimum retention of ammonia in the formulation, and in that manner minimize its odor. It is once again known, however, that the formulation, the fatty substances contained in it, its emulsifier agents and surfactants, and its viscosity have a substantial influence on coloring performance. When the formulation is modified, a deterioration in coloring performance must therefore in all cases be avoided.
For example, JP 2007191459 proposes the use of cationic surfactants, phosphate esters, and aliphatic alcohols in order to reduce ammonia odor in hair coloring agents.
JP 2003040750 discloses that the ammonia odor in hair-bleaching agents is particularly low when at least 5% of a crystalline component is added to the agents.
Although the literature proposes several methods for reducing the odor impact caused by ammonia, there is nevertheless no known possibility for completely suppressing ammonia odor.